1. Field of the Invention
The present invention relates to a device from which light transmitted through an electrode can be obtained. For example, the invention relates to a light emitting device provided with a light emitting element or a liquid crystal display device.
2. Description of the Related Art
Flat panel displays such as a liquid crystal panel have been improved so as to achieve higher definition images, lower power consumption, and longer life. To put into practical use an electroluminescent panel (hereinafter also referred to as an EL panel) using an electroluminescent element (hereinafter also referred to as an EL element) in a pixel, it is required to realize crisper and brighter display at lower power, utilizing the characteristics of a self light emitting panel. In order to achieve the objective, power efficiency such as current-luminance characteristics of a material used in an EL element has also been improved. However, there are also limitations on the improvements in power efficiency.
The percentage of light produced in a light emitting layer of an EL element that is obtained from a panel (light extraction efficiency) is only approximately 20%. The cause of such low light extraction efficiency is due to that when light produced in a light emitting layer reaches an interface between films having different refractive indices, the light is totally reflected, and the totally reflected light is attenuated while propagating inside the EL element, or the totally reflected light is emitted from a side surface of the light emitting element, for example, an end face of a glass substrate.
Reference 1 (Japanese Published Patent Application No. 2002-278477) discloses an EL element of which light extraction efficiency is increased by reducing the light quantity which is totally reflected. In Reference 1, a low refractive index layer having a refractive index close to that of the air is provided on a surface of a transparent conductive layer on the side from which light is obtained, thereby increasing light extraction efficiency.